1. Field of the Invention
The present invention relates to a rotation preventing mechanism for a scroll-type fluid displacement apparatus.
2. Description of Related Art
Scroll-type fluid displacement apparatus are known in the art. For example, Japanese Patent Application No. 10-44821 describes the construction of the scroll-type fluid displacement apparatus shown in FIG. 1.
The scroll-type fluid displacement apparatus includes two scroll membersxe2x80x94an orbiting scroll and a fixed scroll, each having an end plate, and a spiroidal or involute spiral wrap element extending from one side of each end plate. The scroll members are maintained at an angular and radial offset, so that both spiral elements interfit to form a plurality of line contacts between their spiral curved surfaces to thereby seal off and define at least one pair of fluid pockets. The relative orbital motion of the two scroll members shifts the line contacts along the spiral curved surfaces and, as a result, changes the volume of the fluid pockets. The volume of the fluid pockets increases or decreases depending on the direction of orbital motion. Thus, this scroll-type apparatus is able to compress, expand, or pump fluids.
Referring to FIG. 1, at least a pair of fluid pockets 103 are formed between fixed scroll 101 and orbiting scroll 102. When orbiting scroll 102 is driven with an orbital motion relative to fixed scroll 101, fluid pockets 103 are moved to the center with a consequent reduction in volume, and refrigerant gas confined within fluid pockets 103 is compressed. Ball coupling 115, which prevents orbiting scroll 102 from rotating and transfers thrust load from orbiting scroll 102 to front housing 106, includes first race 116, ball rolling grooves 116a, second race 117, ball rolling grooves 117a, balls 118. First race 116, which is ring-shaped and is fixed to orbiting scroll 102, includes a plurality of ball rolling grooves 116a formed on a circumference thereof at an angular interval. Second race 117, which is ring-shaped and is fixed to front housing 106, includes a plurality of ball rolling grooves 117a formed on a circumference thereof at an angular interval. A plurality of balls 118 are positioned between ball rolling grooves 116a and ball rolling grooves 117a. An interior circular portion of first race 116 contacts an interior circular portion of an end plate of orbiting scroll 102, and a clearance is created between an exterior circular portion of the end plate of orbiting scroll 102 and an exterior circular portion of first race 116. An exterior circular portion of second race 117 contacts an exterior circular portion of an end surface of front housing 106, and a clearance is created between an interior circular portion of front housing 106 and an interior circular portion of second race 117.
In this known compressor, front housing 106 and rear housing 104 are assembled, such that first race 116 and second race 117 are elastically deformed like a coned disk spring, which is a circular plate spring having a hole in the center portion. Therefore, elasticity is created between first race 116 and second race 117, and a connecting force toward the x-axis is generated between fixed scroll 101 and orbiting scroll 102. As a result, a spacer, which is inserted between front housing 106 and rear housing 104 to generate an appropriate force between fixed scroll 101 and orbiting scroll 102, may be no longer required, and the number of parts of the compressor may be reduced.
In this known compressor, however, first race 116 and second race 117 are supported like cantilever. Therefore, when the thrust load, which is transferred from orbiting scroll 102 to front housing 106 through ball coupling 115, increases, the amount of elastic deformation of first race 116 and second race 117 may become excessive. As a result, rolling of balls 118 may lose stability, and the orbiting motion of orbiting scroll 102 may become unstable. Therefore, in this known compressor, the efficiency of compression may be reduced, and wear may occur because a clearance between a top end of a spiral wall of fixed scroll 101 and a top end of a spiral wall of orbiting scroll 102 may increase or decrease.
An object of the present invention is to provide a scroll-type fluid displacement apparatus which includes fewer parts than known configurations, and maintains stability of the orbital motion of an orbiting scroll during high thrust load.
In an embodiment, a ball coupling component for use in a scroll-type fluid displacement apparatus comprises a first race and a second race and a plurality of balls. The first race is fixed to a second side of an end plate of an orbiting scroll. The second race is fixed to an end surface of a front housing, which opposes the second side of the end plate of the orbiting scroll. The balls are positioned between a plurality of ball rolling grooves formed on a circumference of the first race at an angular interval and a plurality of ball rolling grooves formed on a circumference of the second race. An interior circular portion and an exterior circular portion of the first race is connected to the second side of the end plate of the orbiting scroll. A clearance is created between the ball rolling grooves of the first race and the end plate of the orbiting scroll. An interior circular portion and an exterior circular portion of the second race is connected to the end surface of the front housing. A clearance is created between the ball rolling grooves of the second race and the end surface of the front housing.
In another embodiment, a scroll-type fluid displacement apparatus comprises a rear housing and a front housing, a fixed scroll and an orbiting scroll, a driving mechanism, and a ball coupling. The rear housing has an open end and an inlet port and outlet port. A front housing closes the opening of the rear housing. The fixed scroll has a first end plate and a spiral element formed on and extending from a first side of the first end plate. The fixed scroll is attached to the rear housing. The orbiting scroll has a second end plate and a spiral element formed on and extending from a first side of the second end plate. Each of the spiral elements interfits at an angular and a radial offset to form a plurality of line contacts defining at least one pair of sealed-off fluid pockets. A driving mechanism includes a drive shaft rotatably supported by the front housing to effect the orbital motion of the orbiting scroll by rotation of the drive shaft to thereby change the volume of the fluid pockets. A disk-shaped eccentric bushing is rotatably connected to a crank pin on a disk, which is formed integrally with the drive shaft. A radial bearing is fitted into an annular boss formed on the second side of the end plate of the orbiting scroll and receives the disk-shaped eccentric bushing. A ball coupling includes an first race fixed to the second side of the end plate of the orbiting scroll and a second race fixed to an end surface of the front housing and a plurality of balls. The first race and the second race face each other. The balls are positioned between a plurality of all rolling grooves formed on a circumference of the first race at an angular interval and a plurality of ball rolling grooves formed on a circumference of the second race at an angular interval. An interior circular portion and an exterior circular portion of the first race are connected to the second side of the end plate of the orbiting scroll. A clearance is created between the ball rolling grooves of the first race and the second side of the end plate of the orbiting scroll. An interior circular portion and an exterior circular portion of the second race are connected to the end surface of the front housing. A clearance is created between the ball rolling grooves of the second race and the end surface of the front housing.
The structure for the scroll-type fluid displacement apparatus according to this invention may no longer require a spacer, which is inserted between the front housing and the rear housing to generate an appropriate force between the fixed scroll and the orbiting scroll, and the number of the parts of the scroll-type fluid apparatus may be reduced. Further, the structure for the scroll-type fluid displacement apparatus according to this invention may permit stable movement of the orbiting scroll in an orbital motion.
Other objects, features, and advantages will be apparent to persons of ordinary skill in the art from the following detailed description of the invention and the accompanying drawings.